Fuel efficiency requirements for passenger vehicles are becoming increasingly more stringent. New legislation in the United States and European Union within the past few years has set fuel economy and emissions targets not readily achievable with today's vehicle and lubricant technology.
To address these increasing standards, automotive original equipment manufacturers are demanding better fuel economy as a lubricant-related performance characteristic, while maintaining deposit control and oxidative stability requirements. One well known way to increase fuel economy is to decrease the viscosity of the lubricating oil. However, this approach is now reaching the limits of current equipment capabilities and specifications. At a given viscosity, it is well known that adding organic or organic metallic friction modifiers reduces the surface friction of the lubricating oil and allows for better fuel economy. However these additives often bring with them detrimental effects such as increased deposit formation, seals impacts, or they out-compete the anti-wear components for limited surface sites, thereby not allowing the formation of an anti-wear film, causing increased wear.
Contemporary lubricants such as engine oils use mixtures of additives such as dispersants, detergents, inhibitors, viscosity index improvers and the like to provide engine cleanliness and durability under a wide range of performance conditions of temperature, pressure, and lubricant service life.
Lubricant-related performance characteristics such as high temperature deposit control and fuel economy are extremely advantageous attributes as measured by a variety of bench and engine tests. As indicated above, it is known that adding organic friction modifiers to a lubricant formulation imparts frictional benefits at low temperatures, consequently improving the lubricant fuel economy performance. At high temperatures, however, adding increased levels of organic friction modifier can invite high temperature performance issues. For example, engine deposits are undesirable consequences of high levels of friction modifier in an engine oil formulation at high temperature engine operation.
A major challenge in engine oil formulation is simultaneously achieving high temperature deposit control while also achieving improved fuel economy.
Despite the advances in lubricant oil formulation technology, there exists a need for an engine oil lubricant that effectively improves fuel economy while maintaining or improving friction reduction properties and deposit control.